In the field of motor vehicles it is well known that the voltage supplied to the on-board electrical system can be maintained at a predetermined set value by means of a regulating device known as a “regulator”, independently of the rotation speed of the engine or the electrical consumption of the equipment.
At the present time motor vehicle equipment manufacturers have developed very high performance alternators using electronic power systems controlled by circuits using digital techniques, based in particular on the use of wired logic, microprocessors or microcontrollers.
Unlike former two-blade regulators which operated around a fixed regulated voltage regardless of the manner in which the vehicle was functioning, modern electronic regulation devices make use of electronic signal processing capabilities to receive variable set values transmitted by an engine control unit in order to optimise battery charge and generation of the electricity required for electronic equipment in relation to torque.
It is envisaged that the alternator should not draw torque when the engine is started, or when accelerating, in order to improve the performance of vehicles of small cylinder capacity, or chat the torque drawn may be further reduced because the battery is already loaded.
It is known that the resistant torque drawn by an alternator can be limited by a progressive load function known as “LRC” (acronym for the English phrase “Load Response Control”).
In particular the LRC function prevents the internal combustion engine from stopping when it is idling or cold, when the vehicle is starting, and when major electrical loads are connected to the on-board electrical system.
Without the LRC function connection of these loads would cause the voltage regulator of the PWM (“Pulse Width Modulation”) type to increase the duty cycle with as a consequence an increase in the excitation current feeding the alternator rotor, and as a result increasing the resistant torque.
The LRC function generally limits this duty cycle on the basis of variables such as the rotation speed of the engine (i.e. of the thermal combustion engine), or the temperature, or the excitation current, or the feed voltage.
For example, the process of progressively controlling the load on a motor vehicle alternator disclosed in European patent application EP2259421 defines the maximum permitted value for the duty cycle in relation to an alternator rotation speed.
However the ways in which the LRC function is implemented known in the state of the art, which take into account only one decision variable, have weakness in some situations, for example when it is not desired to exceed a torque value.